Question

Food grains are stored in ____________________ storage.

2. Which of the following is a thermosetting plastic?
(a) Polythene            (b) Melamine            (c) Teflon                     (d) PVC

3. The SI unit of frequency of sound is ____________.

4. What is the meaning the following terms? 
a) Vibration                   b) Amplitude             c) Frequency

5.Suggest three measures to limit noise pollution in your locality.

6.Two astronauts are floating close to each other in space. Can they talk to each other without using any special device? Give reasons.​

Answer 1

Food grains are stored on granaries

Answer 2

1. Food grains are stored in cold storage (granaries).

Explanation:

1. Food grains are stored in cold storage (granaries).

2. Which of the following is a thermosetting plastic?

   answer: b)  Melamine

3. The SI unit of frequency of sound is hertz (Hz).

4. What is the meaning the following terms?

 a) Vibration : Vibration is defined as a rapid to and fro or up and down movement about a mean position.

b) Amplitude : The amplitude of a sound wave is the measure of the height of the wave. The amplitude of a sound wave can be defined as the loudness or the amount of maximum displacement of vibrating particles of the medium from their mean position when the sound is produced.

 c) Frequency : The number of oscillations per second is known as the frequency of oscillation. Its unit is hertz and is denoted by Hz.

5. Three measures to limit noise pollution are:

• Use less Horns while driving.
• We should use Loudspeakers at low volume and should not play music too loudly during parties.
• Trees should be planted along the roads and around buildings.

6. No, they cannot talk without using any special device.

Sound waves need molecules to propagate as they are longitudinal waves, so they need a medium to travel through.  

When the two astronauts are floating close to each other in space, without the use of any special device, they cannot talk to each other because there is vacuum between them. As there is vacuum, it means there are no molecules or particulate matter between them for the sound to travel. So they cannot talk to each other.